Package for high-power semiconductor devices

ABSTRACT

Methods and apparatuses for forming a package for high-power semiconductor devices are disclosed herein. A package may include a plurality of distinct thermal spreader layers disposed between a die and a metal carrier. Other embodiments are described and claimed.

TECHNICAL FIELD

Embodiments of the present invention relate generally to microelectronicdevices including packages for high-power semiconductor devices.

BACKGROUND

In the current state of technology, there has been an increased demandfor devices with high power density. The requirements for devices suchas microwave- and millimeter-wave devices, for example, are becomingincreasingly stringent. To accommodate such demands, gallium nitridetechnology has been used with favorable results. Problematic, however,is the heat output with the high power densities associated with galliumnitride.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings. To facilitate this description, like reference numeralsdesignate like structural elements. Embodiments of the invention areillustrated by way of example and not by way of limitation in thefigures of the accompanying drawings.

FIG. 1 illustrates a package in accordance with various embodiments ofthe present invention.

FIG. 2 is a flowchart depicting operations of manufacturing a package inaccordance with various embodiments of the present invention.

FIGS. 3( a), 3(b), 3(c), 3(d), and 3(e) illustrate a schematic ofmanufacturing operations of a package in accordance with variousembodiments of the present invention.

FIG. 4 is a flowchart depicting operations of manufacturing a package inaccordance with various embodiments of the present invention.

FIGS. 5( a), 5(b), 5(c), 5(d), 5(e), and 5(f) illustrate a schematic ofmanufacturing operations of a package in accordance with variousembodiments of the present invention.

FIG. 6 is a block diagram of an exemplary radio frequency system inaccordance with various embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the invention may be practiced. It isto be understood that other embodiments may be utilized and structuralor logical changes may be made without departing from the scope of thepresent invention. Therefore, the following detailed description is notto be taken in a limiting sense, and the scope of embodiments inaccordance with the present invention is defined by the appended claimsand their equivalents.

Various operations may be described as multiple discrete operations inturn, in a manner that may be helpful in understanding embodiments ofthe present invention; however, the order of description should not beconstrued to imply that these operations are order dependent. Moreover,some embodiments may include more or fewer operations than may bedescribed.

The description may use the phrases “in an embodiment,” “inembodiments,” or “in various embodiments,” which may each refer to oneor more of the same or different embodiments. Furthermore, the terms“comprising,” “including,” “having,” and the like, as used with respectto embodiments of the present invention, are synonymous.

For the purposes of the present invention, the phrase “A or B” means“(A), (B), or (A and B).”

Various embodiments of the present invention are directed to methods andapparatuses for forming a package for high-power semiconductor devices.In particular, in accordance with some embodiments, a package is taughtthat includes a plurality of distinct thermal spreader layers disposedbetween a die and a metal carrier. Relative to various methods known inthe related art, these embodiments may decrease thermal resistancebetween dies and a heat sink. These embodiments may additionally oralternatively reduce the presence or severity of localized hot spotsthat may be associated with areas of the die that have relatively higherpower densities.

FIG. 1 illustrates a package 100 in accordance with some embodiments.The package 100 may include a die 104 coupled with a thermal spreaderlayer 108. The thermal spreader layer 108 may be coupled with a thermalspreader layer 112 by an adhesive 116. The thermal spreader layer 112may be further coupled with a metal carrier 120.

The die 104 may be made of a semiconductor material such as galliumnitride (GaN). GaN has a high bandgap relative to other semiconductormaterials and, therefore, may operate at relatively higher voltages andprovide relatively higher power densities. Devices utilizing GaN dies,e.g., GaN high electron mobility transistors (HEMT) devices, may be usedin power management, power amplification, or other high-powerapplications. Effective management of thermal energy sourced from theseGaN dies in these high-power applications may provide a correspondingincrease in performance or longevity of the devices. While embodimentsdescribe the die 104 as a GaN die, the dies of other embodiments mayinclude other semiconductor materials such as, but not limited to,gallium arsenide (GaAs), indium phosphide (InP), or silicon.

As will be readily understood in the art, the schematic of FIG. 1 is notshown to scale. In some embodiments, the thicknesses of the componentsof the package 100 may be as follows. The die 104 may be approximately1-5 microns thick; the thermal spreader layer 108 may be approximately25-500 microns thick; the thermal spreader layer 112 may beapproximately 25-500 microns thick; and the metal carrier may beapproximately 100-2000 microns thick.

The thermal spreader layers may be composed of materials having highthermal conductivity to facilitate rapid distribution of thermal energysourced from the dies 104 during operation. Materials having suitablyhigh thermal conductivity include diamond (thermal conductivity of about700-2000 Watts per meter Kelvin (W/m·K)), aluminum nitride (AlN)(thermal conductivity of up to about 300 W/m·K), polycrystalline siliconcarbide (poly-SiC) (thermal conductivity of greater than 300 W/m·K,carbon nanofibers (thermal conductivity of 800-2000 or more W/m·K), etc.

The adhesive 116 may be a thermally conductive adhesive such as, but notlimited to, eutectic alloys like gold-tin, gold-germanium, gold-silicon,etc., or epoxies like sintered silver, sintered copper, etc. The thermalspreader layers and the adhesive 116 may provide a channel with a lowthermal resistance so that thermal energy may be rapidly transferredfrom a heat source, for example, the die 104, to a heat sink, forexample, the metal carrier 120.

The metal carrier 120 may be a thermally conductive material that hassufficient bulk and thermal properties to store and gradually dissipateabsorbed thermal energy. In various embodiments, the metal carrier 120may include a metal or metal alloys such as, but not limited to, copper,aluminum, copper-moly, copper-tungsten, aluminum-silicon carbide, etc.

The use of the double layer thermal spreaders, as shown, provides anumber of manufacturing efficiencies, as will be discussed below, aswell as various operating efficiencies. For example, the close proximityof the thermal spreaders to a heat sink, for example, metal carrier 120,may assist with efficient removal of unwanted heat away from thesemiconductor device channel of the die 104. The structure of thepackage 100 may work to reduce total thermal resistance in the channelfrom the die 104 to the metal carrier 120, as well as reduce the risk ofhot-spots on the die 104.

While embodiments describe the use of two thermal spreader layers, otherembodiments may include additional thermal spreader layers. Adhesivelayers may be disposed between the different thermal spreader layers.

While not specifically shown, the package 100 may be further packagedfor wire-bonding and routing or assembled directly on a printed circuitboard, e.g., a motherboard, a daughterboard, an application board, etc.

FIG. 2 is a flowchart depicting an operation 200 to manufacture apackage, for example, package 100, in accordance with some embodiments.FIG. 3 is a schematic that corresponds to the operation 200 inaccordance with some embodiments. At 204 and FIG. 3( a), the operation200 may include providing a thermal spreader layer 308 on asemiconductor material 304. The semiconductor material 304 may be, forexample, GaN and the thermal spreader layer 308 may be, for example,diamond.

The providing at 204 may include forming the thermal spreader layer 308on the semiconductor material 304 or vice versa. Forming a layer onanother layer may include any type of formation process including, butnot limited to, growing, depositing, coupling, etc. In some embodiments,the forming may include a chemical vapor deposition (CVD) process. A CVDprocess may be especially useful in forming a diamond thermal spreaderlayer. In embodiments in which a thermal spreader layer includes diamondformed from a CVD process, it may also be referred to as a CVD diamondthermal spreader layer.

The operation 200 may further include, at 208 and FIG. 3( b), providinga thermal spreader layer 312 on a metal carrier 320. The providing at208 may be similar to, or different from, the providing at 204. Forexample, the providing at 208 may include forming the thermal spreaderlayer 312 on the metal carrier 320 or vice versa.

In some embodiments, the formation of the thermal spreader may depend oncharacteristics of the underlying substrate. For example, formation ofthe thermal spreader layer 308 on the semiconductor material 304 mayvary from the formation of the thermal spreader layer 312 on the metalcarrier 320 due to varying characteristics of the semiconductor material304 and the metal carrier 320. In this manner, the two formationprocesses may be independently improved.

The operation 200 may further include, at 212 and FIG. 3( c), providingan adhesive layer 316 on the thermal spreader layer 308 or the thermalspreader layer 312. In FIG. 3( c), the adhesive layer 316 is shown onthe thermal spreader layer 312; however, in other embodiments, it may beprovided in alternative or additional places, such as, for example, onthe thermal spreader layer 308.

The operation 200 may further include, at 216 and FIG. 3( d), couplingthe thermal spreader layer 308 (and the semiconductor material on whichit is disposed) with the thermal spreader layer 312 (and the metalcarrier on which it is disposed). The coupling of 216 may includeplacing the thermal spreader layer 308 against the adhesive layer 316and the thermal spreader layer 312 and curing the adhesive layer 316.The curing of the adhesive layer 316 may include application ofappropriate amounts of heat and/or pressure.

The operation 200 may further include, at 220 and FIG. 3( e),singulating dies. The singulation of the dies at 220 may be performed byusing mechanical dicing (for example, saw, scribe and break, etc.),laser sawing, plasma dicing, plasma and mechanical hybrid dicing, etc.

FIG. 4 is a flowchart depicting an operation 400 to manufacture apackage, for example, package 100, in accordance with some embodiments.FIG. 5 is a schematic that corresponds to the operation 400 inaccordance with some embodiments. The operation 400 may be similar tooperation 200 except as otherwise noted.

At 404 and FIG. 5( a), the operation 400 may include providing a thermalspreader layer 508 on a semiconductor material 504, such as a GaN wafer.

The operation 400 may further include, at 408 and FIG. 5( b),singulating dies 502(a) and 502(b). Die 502(a) may include asemiconductor portion 504(a) and a thermal spreader portion 508(a).Similarly, die 502(b) may include a semiconductor portion 504(b) and athermal spreader portion 508(b).

The operation 400 may further include, at 412 and FIG. 5( c), providingthermal spreader layer 512 on metal carrier 520.

The operation 400 may further include, at 416 and FIG. 5( d), providingan adhesive layer 516 on the thermal spreader layer 512. In someembodiments, the adhesive layer 516 may be provided on the thermalspreader layer 512 as a pattern including adhesive portions 516(a) and516(b). In some embodiments, the thermal spreader layer 512 may bepatterned by use of a screen or a mask.

The operation 400 may further include, at 420 and FIG. 5( e), couplingthe dies 502 with the thermal spreader layer 512 (and the metal carrieron which it is disposed). This may include a pick-and-place process toplace the dies 502 on the appropriate adhesive portions. Subsequently,the adhesive portions may be cured to securely couple the dies 502 withthe thermal spreader layer 512.

The operation 400 may further include, at 424 and FIG. 5( f), separatingthe singulated dies. The separation of the singulated dies at 424 may beperformed by processes similar to singulation processes used tosingulate the dies at 408. However, the separation operation may be lessprecise in nature allowing for use of cheaper and faster separatingprocesses.

The die-based processing of operation 400 may be associated with higheryields than the wafer-based processing of operation 200, though it mayalso be associated with an extra separation process. The higher yieldsof operation 400 may be provided due to the fact that only the dies thatmeet certain operating criteria, rather than the wafer as a whole, maybe further processed.

The packages described herein may be particularly suitable for GaN HEMTsthat are incorporated into radio frequency systems for power managementor power amplification at various frequencies, for example, microwaveand/or millimeter wave frequencies. FIG. 6 is a block diagram of a RFsystem 600 in accordance with various embodiments. The RF system 600 maybe a wireless communication device that has an RF front-end 604 thatincludes various components to facilitate transmission or reception ofRF signals. The components could include, but are not limited to, anantenna switch module, a transmitter, a receiver, an amplifier, aconverter, a filter, etc.

In addition to the RF front-end 604, the RF system 600 may have anantenna 616, a transceiver 620, a processor 624, and a memory 628coupled with each other at least as shown. The RF system 600 may furtherinclude a power supply 632 coupled to one or more of the othercomponents to provide appropriate power supplies. In variousembodiments, GaN HEMTs (or other devices) packaged in accordance thepresent teachings may be employed in a power management application ofthe power supply 632, an amplification application of the RF front-end604, or other application.

The processor 624 may execute a basic operating system program, storedin the memory 628, in order to control the overall operation of thewireless communication device 600. For example, the processor 624 maycontrol the reception of signals and the transmission of signals by thetransceiver 620. The processor 624 may be capable of executing otherprocesses and programs resident in the memory 628 and may move data intoor out of the memory 628 as desired by an executing process.

The transceiver 620 may receive outgoing data (e.g., voice data, webdata, e-mail data, signaling data, etc.) from the processor 624, maygenerate RF signal(s) to represent the outgoing data, and provide the RFsignal(s) to the RF front-end 604. Conversely, the transceiver 620 mayreceive RF signals from the RF front-end 604 that represent incomingdata. The transceiver 620 may process the RF signals and send incomingsignals to the processor 624 for further processing.

The RF front-end 604 may provide various front-end functionality. Thefront-end functionality may include, but is not limited to, switching,amplifying, filtering, converting, etc.

In various embodiments, the antenna 616 may include one or moredirectional and/or omnidirectional antennas, including a dipole antenna,a monopole antenna, a patch antenna, a loop antenna, a microstripantenna, or any other type of antenna suitable for transmission and/orreception of RF signals.

In various embodiments, the wireless communication device 600 may be,but is not limited to, a mobile telephone, a paging device, a personaldigital assistant, a text-messaging device, a portable computer, adesktop computer, a base station, a subscriber station, an access point,a radar, a satellite communication device, or any other device capableof wirelessly transmitting/receiving RF signals.

Those skilled in the art will recognize that the RF system 600 is givenby way of example and that, for simplicity and clarity, only so much ofthe construction and operation of the RF system 600 as is necessary foran understanding of the embodiments is shown and described. Variousembodiments contemplate any suitable component or combination ofcomponents performing any suitable tasks in association with the RFsystem 600, according to particular needs. Moreover, it is understoodthat the RF system 600 should not be construed to limit the types ofdevices in which embodiments may be implemented.

Although certain embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent embodiments or implementations calculated toachieve the same purposes may be substituted for the embodiments shownand described without departing from the scope of the present invention.Those with skill in the art will readily appreciate that embodiments inaccordance with the present invention may be implemented in a very widevariety of ways. This application is intended to cover any adaptationsor variations of the embodiments discussed herein. Therefore, it ismanifestly intended that embodiments in accordance with the presentinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. An apparatus comprising: a metal carrier; a firstthermal spreader layer coupled with the metal carrier; a second thermalspreader layer coupled with the first thermal spreader layer by anadhesive, wherein the first and second thermal spreader layers arecomposed of the same material; and a die coupled with the second thermalspreader layer.
 2. The apparatus of claim 1, wherein the first andsecond thermal spreader layers are chemical vapor deposition diamondlayers.
 3. The apparatus of claim 1, wherein the die is a galliumnitride die.
 4. The apparatus of claim 1, wherein the first and secondthermal spreader layers comprise polycrystalline silicon carbide,aluminum silicon carbide, or aluminum nitride.
 5. The apparatus of claim1, wherein the metal carrier comprises copper or aluminum.
 6. Theapparatus of claim 1, wherein the first spreader layer has a thicknessbetween 25 and 500 microns and the second spreader layer has a thicknessbetween 25 and 500 microns.
 7. A system comprising: a radio frequency(RF) front end configured to transmit or receive radio frequencysignals; a power supply coupled with the RF front end to provide powerto the RF front end; and a gallium nitride (GaN) high electron mobilitytransistor (HEMT) device in the RF front end to provide poweramplification or in the power supply to provide power management, theGaN HEMT including: a GaN die; a plurality of thermal spreader layerscoupled with the GaN die; an adhesive layer coupled between individualthermal spreader layers; and a metal carrier coupled with the pluralityof thermal spreader layers.
 8. The system of claim 7, wherein theplurality of thermal spreader layers comprise chemical vapor depositiondiamond.